Average Weather in October at Napa County Airport California, United States
Daily high temperatures decrease by 8°F, from 79°F to 70°F, rarely falling below 62°F or exceeding 90°F.
Daily low temperatures decrease by 4°F, from 50°F to 46°F, rarely falling below 38°F or exceeding 56°F.
For reference, on September 11, the hottest day of the year, temperatures at Napa County Airport typically range from 52°F to 80°F, while on January 1, the coldest day of the year, they range from 39°F to 55°F.
Average High and Low Temperature in October
The figure below shows you a compact characterization of the hourly average temperatures for the quarter of the year centered on October. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature in October
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
The month of October at Napa County Airport experiences very rapidly increasing cloud cover, with the percentage of time that the sky is overcast or mostly cloudy increasing from 19% to 37%.
The clearest day of the month is October 1, with clear, mostly clear, or partly cloudy conditions 81% of the time.
For reference, on January 11, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 56%, while on July 20, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 92%.
Cloud Cover Categories in October
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. At Napa County Airport, the chance of a wet day over the course of October is very rapidly increasing, starting the month at 5% and ending it at 14%.
For reference, the year's highest daily chance of a wet day is 31% on February 20, and its lowest chance is 0% on July 30.
Probability of Precipitation in October
To show variation within the month and not just the monthly total, we show the rainfall accumulated over a sliding 31-day period centered around each day.
The average sliding 31-day rainfall during October at Napa County Airport is rapidly increasing, starting the month at 0.5 inches, when it rarely exceeds 1.3 inches or falls below -0.0 inches, and ending the month at 1.8 inches, when it rarely exceeds 4.1 inches or falls below 0.1 inches.
Average Monthly Rainfall in October
Over the course of October at Napa County Airport, the length of the day is rapidly decreasing. From the start to the end of the month, the length of the day decreases by 1 hour, 10 minutes, implying an average daily decrease of 2 minutes, 21 seconds, and weekly decrease of 16 minutes, 26 seconds.
The shortest day of the month is October 31, with 10 hours, 36 minutes of daylight and the longest day is October 1, with 11 hours, 46 minutes of daylight.
Hours of Daylight and Twilight in October
The earliest sunrise of the month at Napa County Airport is 7:05 AM on October 1 and the latest sunrise is 29 minutes later at 7:34 AM on October 31.
The latest sunset is 6:51 PM on October 1 and the earliest sunset is 41 minutes earlier at 6:10 PM on October 31.
Daylight saving time is observed at Napa County Airport during 2021, but it neither starts nor ends during October, so the entire month is in daylight saving time.
For reference, on June 21, the longest day of the year, the Sun rises at 5:46 AM and sets 14 hours, 50 minutes later, at 8:35 PM, while on December 21, the shortest day of the year, it rises at 7:22 AM and sets 9 hours, 30 minutes later, at 4:52 PM.
Sunrise & Sunset with Twilight and Daylight Saving Time in October
The figure below presents a compact representation of key lunar data for October 2021. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.
Moon Rise, Set & Phases in October
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
The chance that a given day will be muggy at Napa County Airport is essentially constant during October, remaining around 0% throughout.
For reference, on July 18, the muggiest day of the year, there are muggy conditions 0% of the time, while on November 10, the least muggy day of the year, there are muggy conditions 0% of the time.
Humidity Comfort Levels in October
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.
The average hourly wind speed at Napa County Airport is essentially constant during October, remaining within 0.2 miles per hour of 6.5 miles per hour throughout.
For reference, on June 15, the windiest day of the year, the daily average wind speed is 8.2 miles per hour, while on October 29, the calmest day of the year, the daily average wind speed is 6.3 miles per hour.
Average Wind Speed in October
The hourly average wind direction at Napa County Airport throughout October is predominantly from the west, with a peak proportion of 67% on October 1.
Wind Direction in October
Napa County Airport is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.
The average surface water temperature at Napa County Airport is essentially constant during October, remaining within 1°F of 57°F throughout.
Average Water Temperature in October
Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).
The growing season at Napa County Airport typically lasts for 9.9 months (299 days), from around February 14 to around December 10, rarely starting after March 31, or ending before November 13.
The month of October at Napa County Airport is reliably fully within the growing season.
Time Spent in Various Temperature Bands and the Growing Season in October
frigid 15°F freezing 32°F very cold 45°F cold 55°F cool 65°F comfortable 75°F warm 85°F hot 95°F sweltering
Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.
The average accumulated growing degree days at Napa County Airport are increasing during October, increasing by 306°F, from 2,513°F to 2,819°F, over the course of the month.
Growing Degree Days in October
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy at Napa County Airport is rapidly decreasing during October, falling by 1.7 kWh, from 5.2 kWh to 3.5 kWh, over the course of the month.
Average Daily Incident Shortwave Solar Energy in October
For the purposes of this report, the geographical coordinates of Napa County Airport are 38.213 deg latitude, -122.282 deg longitude, and 7 ft elevation.
The topography within 2 miles of Napa County Airport contains only modest variations in elevation, with a maximum elevation change of 253 feet and an average elevation above sea level of 26 feet. Within 10 miles contains only modest variations in elevation (2,192 feet). Within 50 miles contains large variations in elevation (4,705 feet).
The area within 2 miles of Napa County Airport is covered by herbaceous vegetation (42%), cropland (32%), grassland (14%), and artificial surfaces (11%), within 10 miles by grassland (31%) and cropland (22%), and within 50 miles by grassland (23%) and cropland (21%).
This report illustrates the typical weather at Napa County Airport, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
Napa County Airport has a weather station that reported reliably enough during the analysis period that we have included it in our network. When available, historical temperature and dew point measurements are taken directly from this weather station. These records are obtained from NOAA's Integrated Surface Hourly data set, falling back on ICAO METAR records as required.
In the case of missing or erroneous measurements from this station, we fall back on records from nearby stations, adjusted according to typical seasonal and diurnal intra-station differences. For a given day of the year and hour of the day, the fallback station is selected to minimize the prediction error over the years for which there are measurements for both stations.
The stations on which we may fall back include but are not limited to Gnoss Field, Buchanan Field Airport, Travis Air Force Base, Nut Tree Airport, Naval Air Station Alameda (historical), Oakland International Airport, Hayward Air Terminal Airport, and San Francisco International Airport.
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Algorithms 2nd Edition , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for airports and weather stations are provided by AskGeo.com .
Maps are © Esri, with data from National Geographic, Esri, DeLorme, NAVTEQ, UNEP-WCMC, USGS, NASA, ESA, METI, NRCAN, GEBCO, NOAA, and iPC.
The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.
We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.
We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.